The present invention relates to a method for measuring the inertial properties (static moment, frictional moment and moment of inertia) of an aircraft movable control surface. The invention further refers to a mechanical arrangement for operating the cited method.
Aircraft movable control surfaces, such as aircraft elevators, have to be sometimes, under certain circumstances, tested in order to determine whether or not they comply with certain acceptance criteria. Currently, the practical method used for determining the acceptance of a movable control surface is the measurement of its mass and of its center of gravity, these two components allowing the calculation of its static moment, such that this static moment remains within a certain range.
Aircraft movable control surfaces vary slightly their mass, after some period of operation, by water ingestion or by any other matters, or immediately after a damaged unit has been repaired, as these reparations often need extra patches. For this reason, the mass control has to be monitored in time, so that the inertial properties of the movable control surface remain under acceptable limits, as any deviation would affect the dynamic behaviour of the aircraft. Consequently, the control of the inertial properties of the movable control surface is essential.
However, for the known measuring processes of the mass and center of gravity of the movable control surface, the affected unit needs to be removed from the aircraft, which is a cumbersome process requiring long timings and being costly and unpractical, as the process is performed with a crane or other means and needs one hanging scale in each of the hoist points. To get the correct weight of the control surface, it must be unlinked from the aircraft structure such that, when an elevator is measured, for example, the elevator has to be removed from its stabilizer and needs to be lifted with a crane through a sling attached to each of the hoist points, using a hanging scale in each of the hoist points attached to the sling. This task is performed by operators manually, being unpractical, time consuming and expensive.
The present invention proposes a different method of acceptance for aircraft movable control surfaces.